adarshsanjeev commented on code in PR #14660: URL: https://github.com/apache/druid/pull/14660#discussion_r1285330752
########## processing/src/main/java/org/apache/druid/storage/remote/ChunkingStorageConnector.java: ########## @@ -0,0 +1,204 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +package org.apache.druid.storage.remote; + +import com.google.common.base.Predicates; +import org.apache.commons.io.input.NullInputStream; +import org.apache.druid.data.input.impl.RetryingInputStream; +import org.apache.druid.java.util.common.FileUtils; +import org.apache.druid.java.util.common.IOE; +import org.apache.druid.java.util.common.RE; +import org.apache.druid.java.util.common.StringUtils; +import org.apache.druid.storage.StorageConnector; + +import java.io.File; +import java.io.FileInputStream; +import java.io.FileNotFoundException; +import java.io.IOException; +import java.io.InputStream; +import java.io.SequenceInputStream; +import java.util.Enumeration; +import java.util.UUID; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.concurrent.atomic.AtomicLong; + +/** + * An abstract implementation of the storage connectors that download the file from the remote storage in chunks + * and presents the downloaded chunks as a single {@link InputStream} for the consumers of the connector. + * This implementation benefits over keeping the InputStream to the remote source open since we don't require the + * connection to be open for the entire duration. + * Checkout {@link ChunkingStorageConnectorParameters} to see the inputs required to support chunking + */ +public abstract class ChunkingStorageConnector<T> implements StorageConnector +{ + private static final long DOWNLOAD_MAX_CHUNK_SIZE_BYTES = 100_000_000; + + private final long chunkSizeBytes; + + public ChunkingStorageConnector() + { + this(DOWNLOAD_MAX_CHUNK_SIZE_BYTES); + } + + public ChunkingStorageConnector( + final long chunkSizeBytes + ) + { + this.chunkSizeBytes = chunkSizeBytes; + } + + @Override + public InputStream read(String path) throws IOException + { + return buildInputStream(buildInputParams(path)); + } + + @Override + public InputStream readRange(String path, long from, long size) + { + return buildInputStream(buildInputParams(path, from, size)); + } + + public abstract ChunkingStorageConnectorParameters<T> buildInputParams(String path) throws IOException; + + public abstract ChunkingStorageConnectorParameters<T> buildInputParams(String path, long from, long size); + + private InputStream buildInputStream(ChunkingStorageConnectorParameters<T> params) + { + // Position from where the read needs to be resumed + final AtomicLong currentReadStartPosition = new AtomicLong(params.getStart()); + + // Final position, exclusive + long readEnd = params.getEnd(); + + AtomicBoolean isSequenceStreamClosed = new AtomicBoolean(false); + + return new SequenceInputStream( + + new Enumeration<InputStream>() + { + boolean initStream = false; + + @Override + public boolean hasMoreElements() + { + // Checking if the stream was already closed. If it was, then don't iterate over the remaining chunks + // SequenceInputStream's close method closes all the chunk streams in its close. Since we're opening them + // lazily, we don't need to close them. + if (isSequenceStreamClosed.get()) { + return false; + } + // Don't stop until the whole object is downloaded + return currentReadStartPosition.get() < readEnd; + } + + @Override + public InputStream nextElement() + { + if (!initStream) { + initStream = true; + return new NullInputStream(); + } + + File outFile = new File( + params.getTempDirSupplier().get().getAbsolutePath(), + UUID.randomUUID().toString() + ); + + long currentReadEndPosition = Math.min( + currentReadStartPosition.get() + chunkSizeBytes, + readEnd + ); + + try { + if (!outFile.createNewFile()) { + throw new IOE( + StringUtils.format( + "Could not create temporary file [%s] for copying [%s]", + outFile.getAbsolutePath(), + params.getCloudStoragePath() + ) + ); + } + + FileUtils.copyLarge( + () -> new RetryingInputStream<>( + params.getObjectSupplier().getObject(currentReadStartPosition.get(), currentReadEndPosition), + params.getObjectOpenFunction(), + params.getRetryCondition(), + params.getMaxRetry() + ), + outFile, + new byte[8 * 1024], Review Comment: I know this code was only moved, but could you add a comment on why these numbers are chosen? -- This is an automated message from the Apache Git Service. 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